In recent years, in the rolling of hard materials such as electrical steel strips, high tensile strength steel, and stainless steel, the diameters of work rolls have been reduced for the purpose of reducing rolling load. However, the reduction in diameter of work rolls causes insufficient spindle strength and thus requires switching from work-roll drive to intermediate-roll drive. Here, drive tangential forces from those intermediate rolls deflect the work rolls. This has led to a problem in that the deflection distorts the strip shape and makes it impossible to achieve stable rolling. Also even with the work-roll drive, the work rolls will be deflected if the difference in tension is large between the inlet side and the outlet side of the work rolls. This has led to a similar problem in that stable rolling cannot be achieved. For these reasons, there has been a strong demand for a technique of minimizing the deflection of the work rolls.
Patent Literature 1 listed below, for example, discloses a technique addressing the case where intermediate-roll drive is used due to reduction in diameter of work rolls. Specifically, in the technique, each intermediate roll is variably offset so that a tangential force applied to the corresponding work roll by a drive torque of the intermediate roll and a component of a load can be balanced with each other. Also, Patent Literature 1 discloses a method of controlling the amount of offset of the intermediate roll by detecting horizontal deflection of the work roll with a gap sensor.